Water filter cartridge

ABSTRACT

A water filter cartridge is provided for gravity-feed water filtration applications, and includes a granular filter media made from a mixture of titanium dioxide particles interspersed with granular activated charcoal. The granular filter media is placed in a filter housing having an upper inlet opening and a lower outlet opening. A seal may be disposed around an outer periphery of the housing at its upper region, and may include a flange region that flexes upwardly upon insertion of the sidewall into a filter cartridge opening. Optionally, the filter media is arranged in several distinct layers, such as a top media layer that is a mixture of agglomerated nanoparticles of titanium dioxide interspersed with granular activated charcoal, an intermediate media layer in the form of agglomerated nanoparticles of titanium dioxide, and a lower media layer that is another mixture of agglomerated nanoparticles of titanium dioxide interspersed with granular activated charcoal.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims the benefit of U.S. provisionalapplication Ser. No. 62/580,508, filed Nov. 2, 2017, which is herebyincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to water filtration and, moreparticularly, to disposable water filter cartridges for drinking water.

BACKGROUND OF THE INVENTION

Water filter cartridges are commonly used in gravity-feed water filterpitchers, such as to reduce off-tastes, such as from chlorine, in sourcewater from in municipal water supplies, well water, and other commondrinking sources. While such drinking sources, particularly in developedcountries, are generally safe from pathogens including bacteria, cysts,viruses, parasites, protozoa, and the like, these drinking sources maystill contain unsafe levels of heavy metals, pesticides and carcinogenicmatter entering the water from mining operations, waste dumps, farmfields, and even residential neighborhoods.

SUMMARY OF THE INVENTION

The present invention provides a water filter cartridge capable ofremoving arsenic and heavy metals including lead, mercury, cadmium,chromium, copper, nickel and thallium, pesticides, herbicides such asatrazine, and carcinogens such as dibromochloromethane, from sourcewater to levels that are at or below the minimum levels specified by theWorld Health Organization and the U.S. Environmental Protection Agency.The cartridge does this using adsorptive media in the form ofagglomerated nanoparticles of titanium dioxide (TiO₂). The TiO₂ may bedispersed more or less evenly throughout the entire media, or may beused to form media layers in the cartridge, including a layer ofsubstantially only TiO₂, and also in other layers including the TiO₂agglomerated particles interspersed with activated charcoal. Thus,source water contaminated with carcinogens, heavy metals, and othernon-pathogen contaminants can be safely filtered in a gravity-feedfiltration device such as residential water filter pitcher, withoutcomplex and costly filtering devices such as reverse-osmosis systems.

In one form of the present invention, a water filter cartridge includesa filter housing defining a chamber, with a filter media disposed in thechamber. The filter media includes a mixture of particles of titaniumdioxide interspersed with granular activated charcoal. Source waterenters the filter housing through an upper inlet opening and exitsthrough a lower outlet opening, passing through the particles oftitanium dioxide and the granular activated charcoal before exiting thelower outlet opening.

According to one aspect, the filter media includes an intermediate medialayer of agglomerated nanoparticles of titanium dioxide disposed betweentop and bottom media layers, which each include the mixture of titaniumdioxide interspersed with granular activated charcoal.

Optionally, the top media layer includes approximately 2 to 3 grams ofthe titanium dioxide mixed into approximately 30 to 50 grams of thegranular activated charcoal, the intermediate media layer includesapproximately 2 to 3 grams of the titanium dioxide, and the bottom medialayer includes another approximately 2 to 3 grams of the titaniumdioxide mixed into another approximately 30 to 50 grams of the granularactivated charcoal.

According to another aspect, the titanium dioxide is made up ofagglomerated nanoparticles having a nominal grain size of about 250-1180microns (about 16 to 60 mesh). Optionally, the titanium dioxide is inthe form of anatase titania crystal.

According to yet another aspect, the lower outlet opening is sized tolimit a water flow rate through the filter media to approximately 0.3liters per minute. Optionally, the lower outlet opening has an area ofabout 0.03 to about 0.04 square inches, and may be divided into aplurality of separate outlet openings, such as four separate openingseach having an area of about 0.007 to 0.009 square inches.

According to still another aspect, there is an upper filter pad disposedin the chamber below the upper inlet opening and above the filter media,and a lower filter pad disposed in the chamber above the lower outletopening and below the filter media. Optionally, the upper filter padand/or the lower filter pad are 25 to 100 micron filters.

According to another aspect, a seal is disposed around an outerperiphery of the annular upper region. The seal may have a thin flangeregion that extends radially outwardly from the housing sidewall, and isconfigured to flex upwardly upon insertion of the cartridge into afilter cartridge opening of a filter support, and to form a seal whenthe cartridge is inserted into the filter support. Optionally, the sealincludes a rounded annular region that extends radially outwardly fromthe sidewall and is spaced from the thin flange region. The roundedannular region may be positioned above the thin flange region, and therounded annular region may be sized to sealingly engage the filtersupport at the filter cartridge opening.

According to a further aspect, the filter housing has a bottom wall inwhich the lower outlet opening is formed, the bottom wall including anupwardly-facing surface that defines a lower extent of the chamber, witha plurality of spaced-apart upwardly-extending projections configured toengage a lower surface of the lower filter pad and thereby support thelower filter pad above the upwardly-facing surface of the bottom wall.

According to a still further aspect, the filter housing includes a topcover defining the upper inlet opening, and defining an upper extent ofthe chamber.

Optionally, a seal such as an O-ring or a soft flange is disposed aroundan outer perimeter of the filter housing at an upper end portionthereof, with the seal configured to engage an annular surface defininga filter mount of a gravity-feed water filter pitcher.

Thus, the water filter cartridge of the present invention provideseffective adsorption of non-pathogen contaminants such as arsenic andheavy metals, pesticides, and other carcinogens from source water, in amanner that results in filtered water that meets or exceedsrecommendations of the World Health Organization and the U.S.Environmental Protection Agency. This is achieved in a cost-effectivedisposable unit that can operate in a gravity-feed pitcher or reservoir,and is thus suitable for home use, or can be scaled for largerapplications depending on the desired flow rate of filtered water.

These and other objects, advantages, purposes and features of thepresent invention will become apparent upon review of the followingspecification in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of a water filter cartridge in accordancewith the present invention;

FIG. 2 is a side elevation of the water filter cartridge of FIG. 1,shown with its cover removed;

FIG. 3 is a side sectional elevation of the water filter cartridge,taken along section line III-III in FIG. 1;

FIG. 4 is a side sectional elevation of the water filter cartridge,taken along section line IV-IV in FIG. 1;

FIG. 5 is a top sectional plan view of the housing of the water filtercartridge, taken along section line V-V in FIG. 1;

FIG. 6 is a bottom plan view of the water filter cartridge of FIG. 1;

FIG. 7 is a perspective view of another water filter cartridge inaccordance with the present invention;

FIG. 8 is a side elevation of the water filter cartridge of FIG. 7;

FIG. 9 is a side sectional elevation of the water filter cartridge,taken along section line IX-IX in FIG. 7;

FIG. 10 is a top sectional plan view of the housing of the water filtercartridge, taken along section line X-X in FIG. 7; and

FIG. 11 is an exploded perspective view of the water filter cartridge ofFIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings and the illustrative embodiments depictedtherein, a water filter cartridge 10 includes a filter housing 12 withbottom wall 14 and a generally cylindrical or frusto-conical sidewall 16extending upwardly from the bottom wall 14, with a top cover 18 fittedat an open upper end portion 16 a of sidewall 16, such as shown inFIG. 1. Top cover 18 includes or defines a plurality of upper inletopenings or slots 20 through which source water enters an interiorchamber 22 that is defined by housing 12, where a multi-layer filtermedia 24 is contained (FIGS. 3 and 4). Bottom wall 14 includes ordefines a plurality of lower outlet openings 26 (FIGS. 5 and 6) throughwhich filtered water, which has passed through filter media 24, exitsthe chamber 22. Filter media 24 is made up of a combination of titaniumdioxide particles and granular activated charcoal, as will be describedin more detail below, and is capable of removing heavy metals and avariety of pesticides and carcinogenic substances from drinking watersources ranging from municipal water supplies to private wells andcisterns, while also reducing or removing off tastes from chlorine andother additives.

In the illustrated embodiment, filter media 24 has three distinctlayers, such as shown in FIGS. 3 and 4, each of which includesagglomerated nanoparticles of titanium dioxide (TiO₂). Suitable forms oftitanium dioxide include the anatase titania crystal form, havingagglomerated particle sizes of about 250 to 1180 micron (about 16-60mesh), which is available from The Dow Chemical Company of Midland,Mich. However, it will be appreciated that other forms and particlesizes of titanium dioxide may also be selected to give satisfactoryresults, without departing from the spirit and scope of the presentinvention.

Filter media 24 includes a top or first media layer 24 a made up of theaforementioned agglomerated nanoparticles of TiO₂ generally interspersedor mixed with granular activated charcoal, such as coconut huskcharcoal, the granular activated charcoal having particle sizes of about354 to 400 microns (about 40 to 45 mesh). An intermediate or secondmedia layer 24 b comprises a layer of substantially only theaforementioned agglomerated nanoparticles of titanium dioxide (TiO₂)directly below the first media layer 24 a. Located directly belowintermediate media layer 24 b is a bottom or third media layer 24 cthat, like top layer 24 a, is made up of the aforementioned TiO₂generally interspersed or mixed with granular activated charcoal, suchas coconut charcoal, the granular activated charcoal having particlesizes of about 354 to 400 microns (about 40 to 45 mesh). Thus, thecomposition of top media layer 24 a and bottom media layer 24 c may besubstantially the same, with the intermediate media layer 24 b ofsubstantially only TiO₂ separating the top and bottom media layers.

In one embodiment sized for use in a residential or home-use waterfilter pitcher, interior chamber 22 has a height of approximately 3.5inches and an average diameter of approximately 1.84 inches, to define amedia volume of approximately 9.3 cubic inches. This space allows fortop media layer 24 a to include approximately 2 to 3 grams of the TiO₂mixed or interspersed with approximately 30 to 50 grams of granularactivated charcoal, for the intermediate media layer 24 b to be formedfrom approximately 2 to 3 grams of TiO₂, and for the bottom media layer24 c to include approximately 2 to 3 grams of the TiO₂ mixed orinterspersed with approximately 30 to 50 grams of granular activatedcharcoal. However, it will be appreciated that the size of the filtercartridge 10 and the volumes of the filter media and ratios of TiO₂ toactivated charcoal may be scaled up or down for various applications anddesired flow rates, and are not intended to be limited to the volumes,sizes, and ratios described herein.

The mixing of TiO₂ particles with particles of activated coconut huskcharcoal in both the top and bottom media layers 24 a, 24 c allows theactivated charcoal particles to form a three dimensional matrix or“scaffold” supporting the TiO₂ particles in the top and bottom medialayers. This mixture in the top and bottom layers, together withintermediate media layer 24 b formed substantially or entirely of TiO₂particles, ensures that substantially all water molecules andcontaminants contained in the source water will contact TiO₂ particleswhile passing through media 24, while further ensuring that the TiO₂does not congeal to reduce the effectiveness of filtration and/or reducethe flow rate through filter 10 to unacceptable levels.

In addition to filter media 24, there is positioned inside interiorchamber 22 an upper filter pad 28 above filter media 24 and below topcover 18, as shown in FIGS. 3 and 4. Located below filter media 24 andspaced above bottom wall 14 is a lower filter pad 30. Upper and lowerfilter pads 28, 30 may be generally disc-shaped pads made of felt orsimilar material, and provide particulate filtration to about 25 to 100microns (about 120 to 550 mesh). In the illustrated embodiment, upperand lower filter pads 28, 30 are each approximately 1/16^(th) inch thickand have diameters substantially corresponding to the inner diameter ofsidewall 16 near top cover 18 and bottom wall 14, respectively. Eachfilter pad 28, 30 prevents filter media 24 from escaping chamber 22through inlet openings 20 or outlet openings 26. In addition, upperfilter pad 28 filters particulate contaminants larger than about 25 to100 microns from the source water entering inlet openings 20 formed intop cover 18.

To facilitate the flow of filtered water through lower filter pad 30 andout through lower outlet openings 26 in bottom wall 14, an array ofupwardly-extending spikes or projections 32 is formed along anupwardly-facing surface 14 a of bottom wall 14, as best shown in FIGS. 4and 5. Projections 32 have tips that engage and support lower filter pad30 from below, and provide space between lower filter pad 30 and theupwardly-facing surface 14 a of bottom wall 14 for filtered water topass to one of the lower outlet openings 26 and out into a filteredwater reservoir located below or around the exterior of filter 10.

In the illustrated embodiment, there are four outlet openings 26 eachhaving a diameter of approximately 0.052 inch and an area of about 0.007to 0.009 square inches. Thus, in the illustrated embodiment, thecombined areas of the four outlet openings total about 0.03 to 0.04square inches of outlet opening area. The four outlet openings 26 arearranged in a square pattern (i.e., each outlet opening at the corner ofthe square) in which the distance between each outlet opening 26 and thetwo closest other outlet openings 26 is approximately ⅞ inch. However,different numbers and sizes and patterns or arrangements of outletopenings are envisioned. In typical gravity-feed residential waterfilter pitchers, the herein-described outlet openings 26 and filtermedia 24 result in a water flow rate through filter 10 of about 0.3liters per minute, with the outlet openings 26 restricting the flow rateto that level. That is, water can pass through the above-describedfilter media 24 and both filter pads 28, 30 at flow rates greater thanabout 0.3 liters per minute if larger outlet openings are used, but whenoutlet openings 26 are sized as described above, the outlet openings 26limit the flow rate and help to ensure that substantially all watermolecules and contaminants contact the agglomerated particles of TiO₂ inone or more of the filter media layers 24 a-c.

Other features of water filter cartridge 10 include a sealing O-ring 34that is received in an annular notch 36 that faces radially outwardlyand is formed in an outer surface of housing sidewall 16 near an upperend thereof (FIGS. 2-4). O-ring 34 provides an enhanced water-tight sealbetween the filter housing sidewall 16 and a circular opening formed atthe bottom of a source water reservoir in a water filter pitcher orother filtering device, and helps to ensure that unfiltered source waterwill not enter the filtered water reservoir or discharge area. Inaddition, a notch 16 a formed in filter housing sidewall 16 providesclearance for certain types of residential gravity-feed water filterpitchers, to facilitate use of cartridge 10 as a substantially universalreplacement cartridge for many different types of water filter pitchers.

Top cover 18 includes an upwardly-extending gripping tab 38 thatfacilitates holding the water filter cartridge 10 during insertion intoa water filter pitcher, and facilitates gripping and removing the waterfilter cartridge 10 from a water filter pitcher, including disengagingthe O-ring 34 (or other sealing feature) that provides an enhanced seal.Top cover 18 further includes four radially outwardly-extending arms 40,as shown in FIGS. 1, 3 and 4, which are used to secure top cover 18 tothe open upper end defined by cartridge sidewall 16. In the illustratedembodiment, arms 40 are arranged at 90 degrees and 180 degrees relativeto one another, and engage respective blocking projections 42 andblocking-latching projections 44 formed at the top of cartridge sidewall16. Blocking projections 42 are positioned opposite one another and areengaged by two of the arms 40 upon counterclockwise rotation (viewedfrom above) of top cover 18 relative to cartridge sidewall 16.Blocking-latching projections 44 include upwardly-extending portions 44a that are engaged by the two other arms 40 upon counterclockwiserotation of top cover 18 relative to cartridge sidewall 16, and furtherinclude circumferentially-extending legs 44 b that project laterallyfrom upper ends of the upwardly-extending portions 44 a. Thecircumferentially-extending legs 44 b cover portions of the arms 40 thatrotate into engagement with the upwardly-extending portions 44 a.

Optionally, and as shown in FIGS. 1-4, the blocking-latching projections44 are made of resilient material and the circumferentially-extendinglegs 44 b include latching features that resist clockwise rotation oftop cover 18 once legs 40 fully engage the circumferentially-extendinglegs 44 b. This engagement permits top cover 18 to be initiallymechanically secured to the filter housing sidewall 16 after chamber 22is filled with filter media 24 and filter pads 28, 30. Although it maybe sufficient to mechanically secure top cover 18 in this manner alone,it is further envisioned that top cover 18 may be further secured, suchas permanently, via ultrasonic welding or other techniques, so thatcartridge housing 12 may not be disassembled by removing top cover 18from the open upper end of the cartridge sidewall 16. Cartridge housing12, including bottom wall 14, projections 32, sidewall 16, and top cover18, may all be made from molded resinous plastic or substantially anyother suitable material that is suitable for use in direct contact withdrinking water.

During assembly, top cover 18 may apply a compressive force to upperfilter pad 28, which results in a compressive force applied to filtermedia 24 and lower filter pad 30, and prevents or limits the filtermedia layers 24 a-c from mixing with one another during transportation,handling, and use. In this way, filter media layers 24 a-c aremaintained as substantially discrete layers, even if no porous membraneor screen is positioned between adjacent layers. However, it will beappreciated that, if desired, a porous membrane or filter pad or screenmay between the upper media layer 24 a and intermediate media layer 24b, and between the intermediate media layer 24 b and the lower medialayer 24 c, without departing from the spirit and scope of the presentinvention. In addition, although a three-layer filter media is primarilydescribed herein, it will be appreciated that additional layers, ordifferent arrangements or ordering or dimensioning of layers, ordifferent ratios of the constituents of each filter media layer, may beselected to provide desired filtration and flow rates.

The following is an example of the filtration performance provided bygravity-feed water filter cartridges configured as described above.Contaminated source water was provided, having arsenic at 50 parts perbillion (ppb), lead at 150 ppb, mercury at 15 ppb, cadmium at 15 ppb,and chromium at 15 ppb. The filtered water exiting the water filtercartridges contained less than 4 ppb arsenic (EPA limit 10 ppb), lessthan 3 ppb lead (EPA limit 15 ppb), less than 0.2 ppb mercury (EPA limit2 ppb), less than 4 ppb cadmium (EPA limit 5 ppb), and less than 10 ppbchromium (EPA limit 100 ppb).

Although the layered media of water filter cartridge 10 has been foundto provide good performance, it may be possible to achieve similarperformance using a non-layered filter media, such as with asubstantially homogenous media 124 of an alternative water filtercartridge 110 (FIGS. 7-11). Because of the non-layered media 124, asimplified top cover arrangement, and a molded-on seal, the productioncosts of the alternative cartridge 110 may be reduced as compared to thecartridge 10 of FIGS. 1-6. In many respects this alternative waterfilter cartridge 110 is similar or nearly identical to the water filtercartridge 10 described above, such that the following discussion of thealternative cartridge 110 will focus primarily on the differencesbetween the cartridges. It will be appreciated that various regions andcomponents of cartridge 110 that are substantially similar to regionsand components of cartridge 10 are given like numerals by the additionof 100, such that the regions and components may be generally understoodwith reference to the above discussion.

The homogenous media cartridge 110 includes a filter housing 112 that issubstantially similar to the housing 12 described above, but with adifferent mating interface for the top cover 118 to the filter housingsidewall 116, and with a sealing member in the form of an integralflange seal 134 instead of the separate O-ring 34 of cartridge 10. Topcover 118 has a generally flat annular rim 140 with a pair of holes 142formed at opposite sides thereof, such as shown in FIGS. 7, 9 and 11.Holes 142 receive respective pins 144 that project upwardly from anupper rim of the filter housing sidewall 116, such as shown in FIG. 11.Once the top cover 118 is assembled to the sidewall 116 as shown inFIGS. 7-9, the upper ends of the pins 114 may be expanded by a swagingor heat-staking operation, causing the pins' upper ends to expand sothat they cannot be pulled back through the holes 142. Optionally, theentire annular lower surface of the top cover's annular rim 140 can beultrasonically sealed or secured in any suitable manner to the upper rimof the filter housing sidewall 116.

Top cover 118 includes an upwardly-extending gripping tab 138 and apattern of source water entry holes 120 that, in one exemplaryembodiment, may be sized at about 0.052 inches in diameter. The topcover 118 further includes the annular sealing member or seal 134 at itsouter perimeter. The seal 134 can be made from any natural or syntheticrubber or rubber-like material that is suited and approved for extendedcontact with potable water and dissolved substances and solids that arecommonly found in source water used to generate potable water. Seal 134may be molded directly onto the outer perimeter surface of the filterhousing sidewall 116, just below its upper rim, such as shown in FIGS. 9and 11. Optionally, the seal 134 may be formed as a separate member, andstretched around the upper rim of the sidewall 116 in a separateassembly step.

Seal 134 includes a thin flange region 134 a that flexes upwardly uponinsertion of the cartridge 110 into a filter cartridge opening at thebottom of a source water reservoir of a gravity-feed water filteringpitcher, and establishes a water-resistant or water-tight seal with thesurface defining the filter cartridge opening in the pitcher. The thinflange region 134 a may account for (or extend along) only about 5% to25% of the overall height of the seal 134, and may be sufficiently thinto be membrane-like, while remaining sufficiently resilient to return toits relaxed radially-outwardly extended state, as shown in the drawings,after it is no longer compressed inwardly when installed in a filterpitcher or other filter support. Seal 134 further includes a taller androunded annular upper region 134 b spaced above the thin flange region134 a, and may provide or establish a separate sealing interface abovethe sealing interface provided by the thin flange region 134 a. Becauseof the distance by which the thin flange region 134 a extends radiallyoutwardly from the filter housing sidewall 116, along with thesignificant flexibility of the seal material particularly in the flangeregion 134 a, the seal 134 may be better suited than a traditionalO-ring at accommodating imperfections in the shapes of the filterhousing sidewall 116 and/or the surface defining the filter cartridgeopening in the pitcher (e.g., out-of-round conditions, localized ridges,flashing, etc.). In this way, contaminated source water above thecartridge 110 is substantially or entirely precluded from leaking intothe clean water reservoir below the cartridge.

Referring to FIGS. 9 and 11, filter media 124 is a non-layered mixtureincluding agglomerated nanoparticles of titanium dioxide (TiO₂) areevenly interspersed with refined coconut charcoal, without anydistinguishable layers or regions that are significantly higher inconcentration of TiO₂ or of coconut charcoal. Although it is possibleand anticipated that the TiO₂ will not be perfectly evenly intermixedwith coconut charcoal particles in filter media 124, an even dispersalof TiO₂ is generally the objective of a pre-mixing step prior to fillingof the filter housing 112 with the media 124, such that the TiO₂particles can be considered substantially evenly interspersed with thecoconut charcoal particles inside the housing 112, even if there aresome variations to the concentration of TiO₂ particles throughout themedia. The particle sizes of TiO₂ and coconut charcoal in media 124 maybe the same or similar to the particle sizes described above withreference to the layered media of cartridge 10. It should be appreciatedthat in the exploded view of FIG. 11, media 124 is depicted as a solidmass that, owing to its makeup as a mixture of particles, has assumedthe shape of the interior chamber 122 as defined by interior surfaces ofthe housing 112.

Accordingly, the present invention provides a water filter cartridgethat is sufficiently low in cost to be suitable for home use, andrequires only source water at gravity-feed pressure, while providedeffective filtration of contaminants such as arsenic and heavy metals,pesticides, and other carcinogens. This is achieved in a cost-effectivedisposable unit that can operate in a gravity-feed pitcher or reservoir,and is thus suitable for home use, or can be scaled for largerapplications depending on the desired flow rate of filtered water.Further, although gravity-feed pitchers are envisioned as a costeffective means of providing sufficient drinking water for a family orother small group of people, it will be appreciated that the principlesof the present invention may be adapted for use in pressurized watersystems, in higher-volume systems, and in other, more complex filtrationsystems or arrangements.

Changes and modifications in the specifically-described embodiments maybe carried out without departing from the principles of the presentinvention, which is intended to be limited only by the scope of theappended claims as interpreted according to the principles of patent lawincluding the doctrine of equivalents.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A disposable waterfilter cartridge for use in a residential gravity-feed pitcher, saidwater filter cartridge comprising: a filter housing defining a chamberhaving an upper inlet opening and a lower outlet opening, wherein saidlower outlet opening has a total area of 0.03 to 0.04 square inches andcomprises four separate openings each having an area of about 0.007 to0.009 square inches; and a filter media disposed in said chamber, saidfilter media comprising a granular mixture of at least 6 grams ofagglomerated nanoparticles of anatase titania crystal titanium dioxidehaving a nominal grain size of about 16 to 60 mesh interspersed withless than or equal to 100 grams of granular activated charcoal having anominal grain size of about 45 mesh; wherein said lower outlet openingis sized to limit a flow rate through said filter media of approximately0.3 liters per minute at gravity-feed pressure in the residential waterfilter pitcher.
 2. The water filter cartridge of claim 1, wherein saidagglomerated nanoparticles of anatase titania crystal titanium dioxideare substantially evenly distributed with said granular activatedcharcoal.
 3. The water filter cartridge of claim 1, wherein said filtermedia comprises approximately 6 to 9 grams of said agglomeratednanoparticles of anatase titania crystal titanium dioxide andapproximately 60 to 100 grams of said granular activated charcoal. 4.The water filter cartridge of claim 1, wherein said filter housingcomprises a sidewall having an annular upper region and a seal disposedaround an outer periphery of said annular upper region.
 5. The waterfilter cartridge of claim 4, wherein said seal comprises a thin flangeregion that extends radially outwardly from said sidewall and isconfigured to flex upwardly upon insertion of the sidewall into a filtercartridge opening of a filter support, and to sealingly engage thefilter support at the filter cartridge opening.
 6. The water filtercartridge of claim 5, wherein said seal comprises a rounded annularregion that extends radially outwardly from said sidewall and is spacedfrom said thin flange region.
 7. The water filter cartridge of claim 6,wherein said rounded annular region is positioned above said thin flangeregion, and wherein said rounded annular region is configured tosealingly engage the filter support at the filter cartridge opening. 8.The water filter cartridge of claim 1, further comprising an upperfilter pad disposed in said chamber below said upper inlet opening andabove said filter media, and a lower filter pad disposed in said chamberabove said lower outlet opening and below said filter media.
 9. Thewater filter cartridge of claim 8, wherein said filter housing comprisesa bottom wall in which said lower outlet opening is formed, said bottomwall comprising an upwardly-facing surface that defines a lower extentof said chamber, and said bottom wall further comprising an array ofspaced-apart upwardly-extending spikes having respective upper tipsconfigured to engage a lower surface of said lower filter pad andsupport said lower filter pad above said upwardly-facing surface. 10.The water filter cartridge of claim 1, wherein said filter mediacomprises separate top and bottom media layers of said granular mixtureof agglomerated nanoparticles of anatase titania crystal titaniumdioxide interspersed with granular activated charcoal, and anintermediate media layer of agglomerated nanoparticles of anatasetitania crystal titanium dioxide disposed between said top and bottommedia layers.
 11. The water filter cartridge of claim 10, wherein saidtop media layer comprises approximately 30 to 50 grams of said granularactivated charcoal and approximately 2 to 3 grams of said agglomeratednanoparticles of anatase titania crystal titanium dioxide, said bottommedia layer comprises approximately 30 to 50 grams of said granularactivated charcoal and approximately 2 to 3 grams of said agglomeratednanoparticles of anatase titania crystal titanium dioxide, and saidintermediate media layer consists of approximately 2 to 3 grams of saidagglomerated nanoparticles of anatase titania crystal titanium dioxide.12. The water filter cartridge of claim 1, wherein said granularactivated charcoal comprises coconut charcoal.
 13. A disposable waterfilter cartridge for use in a residential gravity-feed pitcher, saidwater filter cartridge comprising: a filter housing configured for usein a residential gravity-feed pitcher, said filter housing comprising asidewall having an annular upper region and said filter housing defininga chamber having an upper inlet opening and a lower outlet openingformed in a bottom wall, wherein said lower outlet opening comprisesfour separate openings each having an area of about 0.007 to 0.009square inches and a total combined area of 0.03 to 0.04 square inches; afilter media disposed in said chamber, said filter media comprising agranular mixture of at least 6 grams of agglomerated nanoparticles ofanatase titania crystal titanium dioxide interspersed with less than orequal to 100 grams of granular activated charcoal; a seal disposedaround an outer periphery of said annular upper region, said sealcomprising a flange region that extends radially outwardly from saidsidewall and configured to flex upwardly upon insertion of the sidewallinto a filter cartridge opening of a filter support; an upper filter paddisposed in said chamber below said upper inlet opening and above saidfilter media; and a lower filter pad disposed in said chamber above saidlower outlet opening and below said filter media; wherein said bottomwall comprises an upwardly-facing surface that defines a lower extent ofsaid chamber, and an array of spaced-apart upwardly-extending spikeshaving respective upper tips configured to engage a lower surface ofsaid lower filter pad and support said lower filter pad above saidupwardly-facing surface; and wherein said lower outlet opening is sizedto limit a flow rate through said filter media of approximately 0.3liters per minute.
 14. The water filter cartridge of claim 13, whereinsaid seal comprises a rounded annular region that extends radiallyoutwardly from said sidewall and is spaced from said flange region. 15.The water filter cartridge of claim 14, wherein said rounded annularregion is positioned above said flange region, and wherein said roundedannular region is configured to sealingly engage the filter support atthe filter cartridge opening.
 16. The water filter cartridge of claim13, wherein said granular activated charcoal comprises coconut charcoalhaving a nominal grain size of about 45 mesh, and wherein saidagglomerated nanoparticles of anatase titania crystal titanium dioxidehave a nominal grain size of about 16 to 60 mesh.
 17. The water filtercartridge of claim 13, wherein said agglomerated nanoparticles ofanatase titania crystal titanium dioxide are substantially evenlydistributed with said granular activated charcoal.
 18. The water filtercartridge of claim 13, wherein said filter media comprises separate topand bottom media layers of said granular mixture of agglomeratednanoparticles of anatase titania crystal titanium dioxide interspersedwith granular activated charcoal, and an intermediate media layer ofagglomerated nanoparticles of anatase titania crystal titanium dioxidedisposed between said top and bottom media layers.